The broad objective of the newly created Molecular Physiology and Biophysics Unit (MPBU) is to study the molecular structure and function of ion channel proteins using biochemical, molecular biological and biophysical methods. Ion channels are integral membrane proteins that are present in all cells of the human body and are important for a vast array of physiological processes. The voltage-gated potassium and calcium channels are two homologous channels that are a particular focus of the MPBU. These ion channels are important for the generation and processing of electrical signals in the nervous system, regulation of heart contraction and the secretion of hormones that regulate blood sugar. Studies are now underway to address how voltage-gated potassium and calcium channels accomplish the very important biophysical feat of opening and closing in response to changes in the membrane electric field. The MPBU has isolated a peptide toxin from tarantula venom that modifies the way voltage-gated potassium and calcium channels open and close in response to changes in membrane voltage. The laboratory is now using this toxin as a molecular probe to study the voltage-sensing machinery that controls opening and closing of the ion conduction pore.